1. Field of the Invention
The invention relates to paper machine clothing useful for fabrication of belts, employed in the paper making machine.
2. Brief Description of the Prior Art
Papermaking machines are well known in the art. The modern papermaking machine is in essence a device for removing water from the paper furnish. The water is removed sequentially in three stages or sections of the machine. In the first or forming section, the furnish is deposited on a moving forming wire and water drained through the wire to leave a paper sheet or web. The formed web is then carried into a wet press felt section and passed through one or more nip presses on a moving press felt to remove water to form a sheet having a higher solids content. This sheet is transferred to the dryer section of the papermaking machine where dryer felts press the paper sheet to hot steam heated cylinders to further increase the solids content.
On papermaking machines, endless belts are employed in the various sections to carry the sheet or web of paper. There are a wide variety of forms of the endless belts, some fabricated from metal and others from textile material such as cotton, cotton and asbestos, or cotton, asbestos and synthetic fibrous or filamentous materials. The selection of a given material is dependent to some degree upon the use to which the fabric will be put; i.e., as a forming fabric dryer felt, etc. The openness of the belt is dependent upon the internal fabric interstices or voids between lengthwise and cross-wise yarns in the fabric The greater the volume of interstices or voids, the more distant are the yarns from each other. The greater the openness then, the more potential for a lowering of structural integrity and dimensional stability in the screen.
In carrying the formed paper web through the papermaking machine, the belt aids in drying, controls shrinkage of the paper web and prevents cockles. The fabric must possess strength, dimensional stability, resistance to chemical and thermal degradation, resistance to abrasion, and have a functional permeability. In recent years all monofilament structured fabrics have been developed to meet the above-described needs. However, felts fabricated from all monofilament fabrics have heretofore not been entirely satisfactory. Single-layer all monofilament fabrics generally lack the high degree of dimensional stability required for long use. Multilayered all-monofilament fabrics are characterized in part by improved dimensional stability (in comparison to single-layer fabrics), but the higher yarn density results in less openness and air permeability, which is important to efficiency.
The fabric of the present invention is characterized, in part, by a high percentage of open area (30 to about 55 percent). This is novel for a multilayer fabric. The fabric of the invention also possesses the dimensional stability associated with a multilayer fabric.
Although the subject invention is described with reference to its use in particular sections and postions in a papermaking machine, it has use in all positions and sections of papermaking machinery where a fabric of its characteristics is desirable.
It should further be noted that the fabric of this invention can be used as a base fabric in a needled structure and/or one which is further treated and processed.